in 1 cái bảng dùng 1 echo

<?php

$a=8;

$b=2;

$t1 = "<tr><td></td><td>+</td><td>-</td><td>*</td><td>/</td></tr>";

$t2 = "<tr><td>a=$a</td><td rowspan='2'>".($a+$b)."</td><td rowspan='2'>".($a-$b)."</td><td rowspan='2'>".($a*$b)."</td><td rowspan='2'>".($a/$b)."</td></tr>";

$t3 = "<tr><td>b=$b</td></tr>";

$t = "<table width='600' border='1'>".$t1.$t2.$t3."</table>";

echo "$t";

?>